CONCLUSION
The lysozyme-like enzymes present in the style of the mussel Choromytilus meridionalis
are capable of lysing free-living bacteria in the water column adjacent to kelp beds.
Estimates of the biomass of such bacteria through an upwelling-downwelling cycle, and
of the filtration rate of different-sized mussels suggest that free-living bacteria could meet
the estimated nitrogen requirements of the mussels.
However the findings of Stuart and Klumpp (1984), that mussels filter free-living bacteria
of <1 µm diameter with a retention efficiency of less than 40 %, must be taken into
account.
The bacteriolytic activity of the crystalline style is, however, in a remarkable and apparently adaptive equilibrium with the food resources available for exploitation in the water
column during upwelling and downwelling conditions. When upwelling occurs, the water
temperature is approximately 9°C and is poor in phytoplankton. Under these conditions,
lysozyme-like activity is at its maximum and bacteria predominate as a nitrogen-rich
exploitable food resource with a C: N ratio of approximately 3.7. These phases of active
upwelling are interspersed with an opposite flow of phytoplankton-rich warm surface
water which occurs often within 24 hours following an upwelling phase (see Field et al.,
1977). Under these conditions lysozyme-like activity of the crystalline style is at a
minimum. Nutritional requirements are then met by the activity of the carbohydrases in
the crystalline style which are capable of digesting the cell walls of phytoplankton and
thus making protein available from the cell contents, as well as meeting the carbon
requirements of the mussels from a detrital diet (Seiderer et al., 1982).
Whether these adaptive changes in the enzyme activity of the style are induced by the
qualitative differences in particulate matter available in the water column, or by the
abrupt temperature changes associated with the upwelling-downwelling cycle is at present
unknown.
FIELD J.G., JARMAN N.G., DIECKMANN G.S., GRIFFITHS C.L., VELIMIROV B. and ZOUTENDYK P., 1977. Sun,
Waves, seaweed and lobsters : The dynamics of a west-coast kelp bed. 5. Afr. J. Sci. 73 : 7-10.
FIELD J.G., GRIFFITHS C.L., GRIFFITHS R.J., JARMAN N.G., ZOUTENDYK P., VELIMIROV B. and BOWES A.,
1980a. Variation in the structure and biomass of kelp communities along the south-west Cape coast. Trans. R.
Soc. S. Afr. 44(2): 145-203.
FIELD J.G., GRIFFITHS C.L., LINLEY E.A., CARTER R.A. and ZOUTENDYK P„ 1980 b. Upwelling in a
nearshore marine ecosystem and its biological implications. Estuarine and Coastal Marine Science. 11 :
133-150.
FIELD J.G., GRIFFITHS C.L., LINLEY E.A., ZOUTENDYK P. and CARTER R.A., 1981. Wind induced water
movements in a Benguela kelp bed. In : F.A. Richards (ed), Coastal Upwelling. American Geophysical Union,
Washington D.C.
GROVES W.E., DAVIS F.C. and SELLS B.H., 1968. Spectrophotometric determination of microgram quantities of
protein without nucleic acid interference.Analyt. Biochem. 22 : 195-210.
HUTCHINGS L., 1981. The formation of plankton patches at the base of an upwelled plume in the southern
Benguela current. In : F.A. Richards (ed.), Coastal Upwelling. American geophysical Union, Washington D.C.
JOLLÉS P., 1969. Lysozymes : A chapter in molecular biology. Angewandte Chem. 8 : 227-239.
Koop K., NEWELL R.C. and LUCAS M.I., 1982a. Biodegradation and carbon flow based on kelp (Ecklonia
maxima) debris in a sandy beach microcosm. Mar. Ecol. Prog. Ser. 7 ; 315-326.
432
The lysozyme-like enzymes present in the style of the mussel Choromytilus meridionalis
are capable of lysing free-living bacteria in the water column adjacent to kelp beds.
Estimates of the biomass of such bacteria through an upwelling-downwelling cycle, and
of the filtration rate of different-sized mussels suggest that free-living bacteria could meet
the estimated nitrogen requirements of the mussels.
However the findings of Stuart and Klumpp (1984), that mussels filter free-living bacteria
of <1 µm diameter with a retention efficiency of less than 40 %, must be taken into
account.
The bacteriolytic activity of the crystalline style is, however, in a remarkable and apparently adaptive equilibrium with the food resources available for exploitation in the water
column during upwelling and downwelling conditions. When upwelling occurs, the water
temperature is approximately 9°C and is poor in phytoplankton. Under these conditions,
lysozyme-like activity is at its maximum and bacteria predominate as a nitrogen-rich
exploitable food resource with a C: N ratio of approximately 3.7. These phases of active
upwelling are interspersed with an opposite flow of phytoplankton-rich warm surface
water which occurs often within 24 hours following an upwelling phase (see Field et al.,
1977). Under these conditions lysozyme-like activity of the crystalline style is at a
minimum. Nutritional requirements are then met by the activity of the carbohydrases in
the crystalline style which are capable of digesting the cell walls of phytoplankton and
thus making protein available from the cell contents, as well as meeting the carbon
requirements of the mussels from a detrital diet (Seiderer et al., 1982).
Whether these adaptive changes in the enzyme activity of the style are induced by the
qualitative differences in particulate matter available in the water column, or by the
abrupt temperature changes associated with the upwelling-downwelling cycle is at present
unknown.
FIELD J.G., JARMAN N.G., DIECKMANN G.S., GRIFFITHS C.L., VELIMIROV B. and ZOUTENDYK P., 1977. Sun,
Waves, seaweed and lobsters : The dynamics of a west-coast kelp bed. 5. Afr. J. Sci. 73 : 7-10.
FIELD J.G., GRIFFITHS C.L., GRIFFITHS R.J., JARMAN N.G., ZOUTENDYK P., VELIMIROV B. and BOWES A.,
1980a. Variation in the structure and biomass of kelp communities along the south-west Cape coast. Trans. R.
Soc. S. Afr. 44(2): 145-203.
FIELD J.G., GRIFFITHS C.L., LINLEY E.A., CARTER R.A. and ZOUTENDYK P„ 1980 b. Upwelling in a
nearshore marine ecosystem and its biological implications. Estuarine and Coastal Marine Science. 11 :
133-150.
FIELD J.G., GRIFFITHS C.L., LINLEY E.A., ZOUTENDYK P. and CARTER R.A., 1981. Wind induced water
movements in a Benguela kelp bed. In : F.A. Richards (ed), Coastal Upwelling. American Geophysical Union,
Washington D.C.
GROVES W.E., DAVIS F.C. and SELLS B.H., 1968. Spectrophotometric determination of microgram quantities of
protein without nucleic acid interference.Analyt. Biochem. 22 : 195-210.
HUTCHINGS L., 1981. The formation of plankton patches at the base of an upwelled plume in the southern
Benguela current. In : F.A. Richards (ed.), Coastal Upwelling. American geophysical Union, Washington D.C.
JOLLÉS P., 1969. Lysozymes : A chapter in molecular biology. Angewandte Chem. 8 : 227-239.
Koop K., NEWELL R.C. and LUCAS M.I., 1982a. Biodegradation and carbon flow based on kelp (Ecklonia
maxima) debris in a sandy beach microcosm. Mar. Ecol. Prog. Ser. 7 ; 315-326.
432